I am going to put together a small integrated to power some bookshelf speakers in my office. I need probably more than a watt, but certainly not more than 7 or 8. I don't listen very loudly, so power is not the concern -- midrange is.

I have lots of the parts on hand (edcor opt (5K:8), lots of caps, some rectifier tubes, a chassis, sockets, etc.) so all I think I need are a power transformer, and to choose what tubes to use. I would still like to keep costs low, however.

My sense is to use something in between Bas's How To amp (http://boozhoundlabs.com/howto/) a 6sn7 driving a 6v6 and tubelab.com's design (5842 with a plate load ccs and some power tube.) Thus, I'll probably use a ccs on the driver tube, but also perhaps LED bias it. For the power tube, I am thinking about an ultrapath circuit.

For input tubes, I am thinking 6H30 but am quite open to suggestions if there are better choices.

It is for the output tubes that I am having trouble making up my mind. One thought is to just use some tride strapped pentode or something (el34, 6v6, kt88). I also thought that the 807 looked interesting, though i am not sure how much power it can deliver. It is cheap, though, so might be a nice experiment. Another option is to just not muck about and simply use a 300B -- my main rig amps are 300b, so this would be an opportunity to buy some other tubes brands of tubes to swap around, but it is also a bit more that I was hoping to spend -- or perhaps 2a3, though they may not be powerful enough.

I have tried a lot of tubes with the $18 Edcor transformers. I tried all of the usual suspects, 300B, 2A3, 45, 6B4, triode wired 6L6GC, KT-88, EL-34, 6550, and triode wired horizontal sweep tubes, 6LW6, 6CD6, 6AV5, and vertical sweep tubes 6EM7, 6DN7, and a few others that I can't remember now.

My favorite by far was the 6AV5. It is an old octal TV tube that doesn't have a plate cap. Really dynamic sound. Cheap too. I ran them far in excess of their ratings but you can get a few watts without punishing them. Info here:

Bear in mind that anything you make and put in your office is in a work place and therefore comes under the regulations governing electrical equipment in the work place. Things to avoid would be 807 (top cap), mercury rectifiers, unpotted transformers, lack of a conductive cage over the valves, any exposed wiring, etc, etc. Someone completely lacking any imagination whatsoever slapped a nasty "failed" sticker on my Leak TL10 that took ages to remove without damaging the paintwork...

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The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

Besides the usual suspects the 6CK4 is a maybe a nice try also..
Cheap as well..... Pa-12W, Mu-6.6 Ra-1.2k
Maybe best used in push-pull though for anything more than a few watts, sounded like you were going for SE....

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If it's stuck, force it... If it breaks, what the hell, it needed replacement anyways....
Amateurs fixing a fault: they succeed but then discover another fault in addition to the part they just broke....

The HIGHLY linear triode strapped 6V6 mates WELL with your O/P trafo, but it is good for only approx. 2 W. If approx. 4 triode W. is enough, use 7591As. The 7591A is slightly easier to drive than the 6V6. A 5965 section will provide plenty of linear gain in front of either type. The full O/P of a CDP is more than enough to drive either combo into clipping. That meets your need for an "integrated" amp in only 2 stages.

5842's are getting hard to find, my latest designs are using 1/2 of a 12AT7. They are not as good as a 5842, but close. I use 8 to 10 mA of current.

I'll have to look into that. I assume that you mean they are getting hard to find for cheap? Tubesandmore has them for $13, which, if I only need one, is not so bad.

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Originally posted by EC8010 Bear in mind that anything you make and put in your office is in a work place and therefore comes under the regulations governing electrical equipment in the work place.

I should say home office -- just me. That said, safety is a concern as my cat hangs out in there

Quote:

Originally posted by Eli Duttman If approx. 4 triode W. is enough, use 7591As. The 7591A is slightly easier to drive than the 6V6. A 5965 section will provide plenty of linear gain in front of either type. The full O/P of a CDP is more than enough to drive either combo into clipping. That meets your need for an "integrated" amp in only 2 stages.

Thanks, I'll look at those too. My source is a NOS DAC (sometimes AD1865, sometimes TDA1541a) with a grounded cathode 5687 for voltage gain. It seems to put out about what other cd players do.

i happen to own a single ended amp using triode strapped sexy bottle 6v6gt. with just a half of a 6sl7 as driver per side, this amp sings beautifully with my single driver voigt pipe speakers. this low watt amp plays loud even when mated with bookshelf speakers with fullrange drivers.

I have used the 6CK4 in a number of pp and se amplifiers and it is very linear. Sounds very good. It reminds me a lot of the 45 without the expense. A single 6SL7 configured as an SRPP would drive one with aplomb..

A single 6CK4 in SE would net you between 1.5W - 2Wrms depending on transformer impedance - anything designed for a 45 will work well.

A pair in pp into 7.8K (Dyna ST-35 transformer for example) will get you 10Wrms or more.